Lateral airbags are known to protect the occupant of a vehicle in the event of lateral impact. Lateral airbags are provided for example in doors or in the side trims of the vehicle. These lateral airbags spread out and upwards in the event of a crash so that parts of the body lying level with the window are also protected.
The lateral airbags arranged in this way, however, are not suitable to protect the head of the occupant. Therefore airbags are known which are integrated in the vehicle seat. Thus a head restraint with integrated gas bag is known from DE 94 15 511.9 U1. This gas bag extends in the inflated state sideways from the head area and in the forward travel direction. The drawback with an airbag of this kind provided in the seat is that the sensor required for detonation of the gas generator has to be connected to the energy supply of the vehicle through a cable. Since vehicle seats are however in most cases movable and even removable these cables become in the way.
Therefore lateral airbags are also known which are mounted level with the head at the side in the vehicle. Here the gas bag extends between the A- and B-pillar or the B- and C-pillar of the vehicle. In the inflated state the gas bag covers the area of a side window. In the folded state the gas bag is stowed away above the window frame, i.e., it extends along a curve. In this curved position therefore the distance between the fastening points is greater than in the case where the gas bag runs straight in the inflated state. From this there is the need to tauten the gas bag or fastening sections of the gas bag in its inflated position.
To this end it is known from DE 195 19 297 to provide the gas bag on the A-pillar with a cable which runs over a tautening device. This has a guide pulley where the cable is deflected round 180xc2x0. The guide pulley is displaceable by means of a further mechanical device which is electronically controlled whereby the deflected part of the cable is extended and thus a tautening effect is achieved. This tautening device is operated during the inflation process. The drawback here is that a tautening device of this kind means extra mechanical and electronic expense.
Furthermore a lateral airbag is known from WO 94/19215 for protecting the head wherein this airbag likewise extends between two pillars of the vehicle, e.g., between the A and B pillars. The gas bag is tubular and consists of two crisscrossing threads with an elastic material extending inbetween. When the gas bag is not inflated but is stowed in this state above a vehicle window the threads lie practically parallel to each other. After inflation the threads rotate into the main unfolding direction of the gas bag. The diameter of the gas bag thereby increases whilst the length reduces. Thus a tautening effect likewise occurs without special additional mechanical or electronic aids. The drawback here, however, is that the gas bag has to be made from the said special material.
The object of the invention is to achieve a tautening action in an airbag, more particularly a lateral airbag, without additional mechanical devices and the electronics associated therewith and without having to use special material for the gas bag.
The present invention relates to an airbag, more particularly a lateral airbag with a tubular shape, which is connected to at least two points of the motor vehicle and in the non-inflated state is stored in a curved storage area. According to the invention at least one tensioning cord for shortening the unfolded gas bag is provided between the gas bag and a fastening point on the vehicle whereby the tensioning cord can be tautened through the inflating gas bag.
More particularly at least one tensioning cord is provided which is fixed at one end on the gas bag and at the other end on the vehicle whereby the fixing point on the gas bag can be moved together with the gas bag away from the cord""s fixing point on the vehicle as the gas bag inflates.
Furthermore the invention can be designed so that the tensioning cord is fixed at one end to the gas bag and at the other end to the vehicle and that the tensioning cord has at least one guide point on the gas bag which during inflation of the gas bag can be moved away from the point of attachment of the tensioning cord on the gas bag.
With the airbag according to the invention, the movement of part of the gas bag and in particular a movement away from the point of attachment of the tensioning cord on the vehicle or on the gas bag during inflation of the gas bag is thus utilised to tauten the tensioning cord and thus the gas bag as it unfolds. The length of the tensioning cord can remain unchanged or can be shortened as the gas bag unfolds. The advantage of using the movement of the gas bag to tauten the cord is that no additional mechanical devices and associated electronics are required and that the gas bag can be made from conventional materials.
In a first embodiment, it is proposed that the gas bag is bottle-shaped and has inside a tensioning cord which is shorter than the gas bag and is connected at one end in the area of the bottle neck to the gas bag and at the other end in the non-inflated state of the gas bag to the inverted end of same which corresponds to the bottle base wherein the end of the tensioning cord is connected to the vehicle in the area of the bottle neck and the gas bag is connected to the vehicle in the area of its inflation mouth which is set at a distance from the bottle base.
With this embodiment, the distance between the fastening points of the gas bag at the inflation mouth and at the end of the bottle neck during inflation of the gas bag is reduced to the debit of the distance between the inflation mouth and the bottle base in that this distance is increased by the stretching of the gas bag while the bottle neck is simultaneously folded and thereby shortened.
The tensioning cord can both end at the bottle-shaped end of the gas bag and also extend beyond the gas bag and only there be connected to the vehicle.
In a second embodiment, at least one connecting cord or at least one contraction cord is provided which runs at least approximately in the main unfolding direction of the gas bag and is fixed on opposite parts of the gas bag, and the tensioning cord is fixed roughly in the middle of the connecting cord/contraction cord. The point of attachment of the tensioning cord on the connecting cord moves away from the fixing point of the tensioning cord on the gas bag as the gas bag inflates. The displacement path of the point of attachment thereby corresponds to the slack in the tensioning cord which is to be compensated.
It is expedient if the connecting cord is provided approximately in the center of the gas bag and is designed as a closed ring.
In a first design of this embodiment, the connecting cord runs inside the gas bag and the tensioning cord extends out from the gas bag and is connected to the gas bag at the point where it emerges from the same.
In a second design, the connecting and tensioning cords are provided outside of the gas bag and the tensioning cord is guided at the end of the gas bag between this and a shackle. With this design, the tensioning cord is thus not connected to the end of the gas bag but is guided round the same through the shackle.
In a further embodiment, it is proposed that the tensioning cords are formed at their fastening points with the gas bag as guide shackles for each other tensioning cord.
When using a contraction cord which acts similar to the connecting cord, the tensioning cord is connected to opposite ends of the gas bag. The contraction cord is attached to predefined points of the gas bag so that it gathers together individual sections of the gas bag during unfolding and in this way compensates for the slack in the tensioning cord.
In a third embodiment, the tensioning cord is guided at one end of the gas bag in a shackle and in its non-inflated state is connected to the other end of the gas bag which is folded towards the shackle. As the gas bag unfolds, the folded end of the gas bag moves away from the shackle and away from the fastening point of the tensioning cord on the vehicle and thereby transfers this movement to the tensioning cord.
In a further design of this embodiment, it is proposed that each tensioning cord has at least one return lock which prevents the tensioning cord from moving back against the unfolding direction of the gas bag but allows the tensioning cord to move in the unfolding direction of the gas bag and/or that at least one additional support shackle is provided for guiding the tensioning cord in the middle area of the gas bag which is likely to bend.
Providing a return lock or an additional tensioning cord support shackle prevents the tubular gas bag from bending in through the strain of the occupant once it has unfolded. The protection of the occupant would be impaired if the gas bag were to bend inwards.
In a preferred embodiment, the return lock is formed as a guide shackle and is fixed on the gas bag in place of a guide shackle.
Where two tensioning cords are provided, each tensioning cord has a return lock.
Where two tensioning cords are provided criss-crossing each other, it is expedient to provide one double return lock at the cross-over point.
In a preferred embodiment, the return lock has two relatively movable wedges wherein the tensioning cord runs between opposite wedge faces and these can be pressed against each other by at least one elastically deformable fastening means. During unfolding of the gas bag, the tensioning cords press the wedge faces away from each other against the force of the elastically deformable fastening means, and the tensioning cord is drawn along with the end of the gas bag to which it is fixed, and tautens the unfolded gas bag. As the gas escapes from the gas bag at the end of the unfolding process, the wedge faces are pressed against each other under the action of the elastically deformable fastening means. The tensioning cord is thereby fixed at this point. The tensioning cord thereby remains tensioned between its fastening point on the motor vehicle and the wedge faces even if the gas bag collapses as a result of the escaping gas. This substantially prevents the gas bag from bending inwards.
It is expedient if one wedge is arranged fixed while the other wedge is displaceable relative to the fixed wedge and has the elastically deformable fastening means. As elastically deformable fastening means, a draw spring can be provided whose active direction runs substantially opposite the traction direction of the tensioning cord during unfolding of the gas bag.
To increase the clamping action of the wedge faces, it is expedient if the opposing wedge faces have grooves which run at least approximately cross-wise to the direction of movement of the tensioning cord.
In a further design, it is proposed that at least one additional support shackle is provided between the guide shackles or return locks provided at the ends of the gas bag. Where return locks are used, this support shackle represents an additional means for preventing the gas bag from bending in. In the event that guide shackles are used in place of return locks, the support shackle is the sole means for preventing the gas bag from bending in.
In one embodiment, the tensioning cord is guided on the gas bag and in the non-inflated state is connected to the other end of the gas bag which has been folded towards the fastening point on the vehicle.
In a fourth embodiment, the tensioning cord is connected to the gas bag at the site where the gas bag changes shape the most during inflation and is guided from there towards the end of the gas bag in at least one shackle. It is expedient if the site of the greatest change of shape is formed by a peak-like irregularity in the contour of the gas bag which can be provided as an indent or bulge in the gas bag. In the folded state, the shackles, as well as the fastening point of the tensioning cord on the vehicle, are mounted substantially along a straight line. During unfolding, the tensioning cord is drawn along as a result of the irregular airbag contour through the shackles in the direction of the fastening point of the tensioning cord on the gas bag and the slack in the tensioning cord is thereby compensated.
In a fifth embodiment, the gas bag is fixed in the area of its inflation mouth on the vehicle and extends to each side of the inflation mouth. The tensioning cord is fixed at one end inside the gas bag and with its other end runs out of the gas bag where it is connected to the vehicle outside of the gas bag. For assembly, the gas bag is gathered up in the area next to the inflation mouth which is remote from the fastening point of the tensioning cord on the vehicle. During unfolding of the gas bag, the gathered gas bag material expands and thereby draws in a corresponding piece of the tensioning cord. The tensioning cord can in this embodiment be guided to the outside from the gas bag through an outlet opening, valve opening or through the fabric of the gas bag.
In a sixth embodiment, a gas bag which during folding has been wound up through rotation about the unfolding axis is connected to the tensioning cord on the outside by at least one section which is opposite the fastening point of the tensioning cord on the vehicle. During unfolding the gas bag spreads out in the direction of the useful position and thus in the direction of the fastening point of the tensioning cord on the vehicle. At the same time the gas bag turns back into its original alignment and the slack of the tensioning cord winds up over the circumference of the gas bag.
In one embodiment two tensioning cords are provided of which each one is connected to the vehicle in the area of one end of two opposite ends of the gas bag.
The tensioning cords can be substantially non-deformable, but can however also be made from elastically deformable material.
The invention will now be explained with reference to the embodiments shown in the drawings.